Change in the expression levels of proteins secreted by the chondrocyte-associated extracellular matrix (ECM). The gene-expression profile of mesenchymal stem cells (MSCs; n = 2) was analysed by real-time PCR during their differentiation towards chondrocytes in micropellets. (a) Time-course expression of the members of the CCN family of genes. (b) Time-course expression of various MMPs. CCN, connective tissue growth factor (CTGF); cef10/cyr61 and nov; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; MMP, metalloprotease; PCR, polymerase chain reaction.